Investigators believe Alejandra Ramos and Falcaneri Fuentes may have been speeding when their cars crossed the center line and struck the cruiser being driven by Sgt. Edward Tressler.

“One vehicle crossed over the center line and struck Sgt. Tressler’s cruiser straight on on the right-hand side. The other vehicle also crossed over the center line and struck both vehicles, or one or the other. We are still trying to determine what exactly happened,” said State Police Colonel Marian McGovern.

The speed limit in the area was 35 miles per hour.

“We do have a witness report that tells us they were operating side-by-side in an erratic manner at a very high rate of speed, a speed that was estimated at 70 miles per hour,” McGovern said.

Ramos is in critical condition at Massachusetts General Hospital. Fuentes and a passenger were unhurt.

Both face charges of speeding and operating to endanger.

They were also “unlicensed operators,” according to McGovern.

Sgt. Tressler was treated for a wrist injury.

“Here’s an officer, a supervisor, who had just assisted another trooper at a traffic stop just moments before, less than 300 yards before, when he pulled back out onto the road to carry on his business and was struck head-on.”